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NATURAL HISTORY

FLAT-TAILED HORNED LIZARD } Phrynosoma mcallii
FAMILY: Phrynosomatidae

DESCRIPTION: This lizard is small — roughly 3.4 inches from snout to vent — and very flat and wide with a long, broad tail and a dark stripe running down the middle of the back. Six long, horn-like scales project from the back of the head, with the two central horns noticeably longer than the others; pointed scales also protrude from the sides of the jaw and back. Base color is tan, orange-brown, or reddish brown and typically matches the sand on which the lizard lives; the back is marked with rows of dark, circular blotches.

HABITAT: The flat-tailed horned lizard is most often found in desert scrub on sandy flats and valleys with little or no windblown sand, as well as on salt flats and gravelly soils.

RANGE: The flat-tailed horned lizard is endemic to the Sonoran Desert in southern California (San Diego, Riverside, and Imperial counties), Arizona (Yuma County), and northwestern Mexico (Sonora and Baja).

MIGRATION: The flat-tailed horned lizard is nonmigratory.

BREEDING: Mating takes place in spring; clutches of eggs are laid in late spring and early summer, with clutch size ranging from three to 10 eggs. Hatchlings range from three to about four centimeters; two groups of hatchlings may be produced each year in July and September.

LIFE CYCLE: Adult lizards are active and may spend half the day moving; they spend the nighttime hours burrowed under sand. Mid-November through mid-February, adult lizards hibernate in burrows five to 10 centimeters below the surface, though some juveniles remain active during winter; mid-February to March, they emerge from hibernation to mate, which they do throughout the active season.

FEEDING: The flat-tailed horned lizard feeds primarily on ants but will occasionally eat beetles and other insects.

THREATS: Urban and agricultural development, off-road vehicle activity, energy development, military activities, introduction of nonnative plants, pesticide use, and habitat degradation due to Border Patrol and illegal drive-through traffic along the United States-Mexico border pose multiple, significant threats to this species.

POPULATION TREND: The species is considered to be in moderate decline.

Photo © William Flaxington